JP6820367B2 - Position sensor and position sensing method - Google Patents

Description

The present disclosure relates to a position sensor that compensates for the movement of sensor components in any direction that is not aligned with the detection direction. The present disclosure also relates to corresponding methods of sensing location.

Position sensors are typically constructed using simple magnet and magnetic field sensors. When the magnet moves with respect to the magnetic field sensor, the magnetic field sensor generates an output signal indicating the degree of movement. Such position sensors are simple to manufacture and are typically mass-produced. The distance between the magnet and the magnetic field sensor correlates with the magnetic field strength at the sensor.

Although this type of sensor is simple and inexpensive to manufacture, they are very sensitive to stray magnetic fields and magnet inconsistencies. For example, the movement of the magnet in a direction perpendicular to the intended movement of movement will change the magnetic field strength in the magnetic field sensor, thereby affecting the position measurement.

The present disclosure provides a magnetoresistive magnetic field sensor for detecting a position in a particular direction. The sensor includes a plurality of magnetoresistive elements arranged in pairs. The same pair of elements are arranged so that their sensitivity directions are oriented in the same direction. The different pairs of elements are oriented so that their sensitivity directions are oriented differently, preferably substantially perpendicular to the other pair. Reluctance sensors and their sensitivity directions are generally located in a plane perpendicular to the measurement direction of the device. Each pair of elements is arranged in series between the two nodes to form a bridge circuit. As such, the movement of the magnets in the first plane causes substantially equal changes in each pair of elements, thereby compensating for this movement in the output signal.

According to the first aspect, a magnetoresistive position sensor for measuring a position in at least a first direction is provided. The sensor is arranged to detect the movement of the magnet in at least the first direction and the movement of the magnet in the first direction, and to compensate for the movement of the magnet in at least the second direction. It is equipped with a differential magnetic field sensor.

Therefore, the sensor is configured to measure the movement of the magnet in one particular direction, i.e. the detection direction, while the movement of the magnet in at least the second direction is compensated by the differential magnetic field sensor. That is, the sensor compensates for the movement of the magnet in different directions so that any movement in any other direction does not affect the measurement of the movement of the magnet in the detection direction. For example, the magnet may be configured to hang above the sensor and move towards and away from the sensor in the z direction, where the sensor changes the magnetic field strength as the magnet moves in this direction. To measure. The differential magnetic field sensor may then be configured to compensate for changes in magnetic field strength resulting from any lateral movement of the magnet as it moves in the detection direction.

The differential magnetic field sensor may include a plurality of magnetoresistive elements. For example, the magnetoresistive element can be a giant magnetoresistive (GMR) spin valve, a tunnel magnetoresistive (TMR) element, an anisotropic magnetoresistive element (AMR), or any other suitable material that is sensitive to changes in the magnetic field in a particular direction. It may be a magnetoresistive device.

Each of the plurality of magnetoresistive elements may have a sensing direction, and at least the first pair of elements may be arranged so that their sensing directions are aligned. The sensing directions of the plurality of magnetoresistive elements may be arranged in the first plane, and the first plane may be deviated from the first direction. For example, the first plane may be substantially perpendicular to the first direction. At least the second direction may be in the first plane.

By aligning the sensing directions of the pair of magnetoresistive elements, the movement of the magnet in the direction of sensing results in similar or identical changes in resistance, and the pair of magnetoresistive elements results in zero or substantial relative to the sensor output. They are connected in such a way that they bring about zero change. Therefore, by aligning the sensing directions within one particular plane, any movement within that plane can be compensated.

The sensor may further include a second pair of magnetoresistive elements arranged so that their sensing directions are aligned and their sensing directions are offset from the first pair of magnetoresistive elements. The sensing direction of the first pair of magnetoresistive elements may be substantially perpendicular to the sensing direction of the second pair of magnetoresistive elements.

For example, when the detection direction is the z direction, the sensing direction of the magnetoresistive element may be arranged in the xy plane. A pair of magnetoresistive elements aligns their sensing directions in that direction to compensate for movement in the x direction, while another pair of magnetoresistive elements aligns them in that direction to compensate for movement in the y direction. The sensing direction of is may be aligned in that direction.

The plurality of magnetoresistive elements may be arranged in a first plane so that at least the first and second pairs are evenly distributed around the sensor, and each element of each pair of magnetoresistive elements is a sensor. It is arranged on the opposite side of the magnet and at a position equidistant from the magnet. For example, each pair of magnetoresistive elements may be located at opposite corners of the sensor, or they may be centered at the opposite ends of the sensor.

The plurality of magnetoresistive elements may be connected in a bridge arrangement, and the output of the bridge may indicate the movement of the magnet in the first direction. For example, the bridge arrangement may be a Wheatstone bridge circuit.

At least the second direction may be in a first plane that is substantially perpendicular to the first direction, and the output of the bridge arrangement does not indicate the movement of the magnets in the first plane. Therefore, the output of the bridge arrangement only needs to provide an indicator of motion in the first direction, while the differential magnetic field sensor is configured to compensate for any motion in the first plane. That is, the differential magnetic field sensor is configured such that any movement of the magnet in the first plane results in a zero or substantially zero change in output. As such, the output is independent of movement in the first plane unless it is substantially affected by any change in magnetic field strength caused by the lateral movement of the magnet in the first plane.

In some arrangements, the first pair of magnetoresistive elements is connected in series between the first node and the second node, and the second pair of elements is with the first node and the second node. Connected in series between, the output of the bridge circuit is taken from the node between each pair.

In such a case, each of the plurality of magnetoresistive elements may have a sensing direction. The first pair of magnetoresistive elements are arranged so that their sensing directions are aligned, and the second pair of magnetoresistive elements are arranged so that their sensing directions are aligned. Here, the sensing direction of the second pair of magnetoresistive elements is deviated from the sensing direction of the first pair of magnetoresistive elements. For example, the sensing direction of the first pair of magnetoresistive elements may be substantially perpendicular to the sensing direction of the second pair of magnetoresistive elements.

One of the plurality of magnetoresistive elements may be a reference resistor. In some arrangements, the reference resistor may be shielded so that its output is not magnetic field dependent.

According to a further aspect, a method of measuring a position in at least a first direction using a magnetoresistive position sensor is provided. The method uses a differential magnetic field sensor to detect the position of the magnet in the first direction and uses the differential magnetic field sensor to compensate for the movement of the magnet in at least the second direction. ,including.

At least the second direction may be in the first plane, which is substantially perpendicular to the first direction.

According to the third aspect, a position sensor configured to perform the method of the second aspect is provided.

According to a fourth aspect, a sensor magnetoresistive position sensor for measuring a position in at least a first direction is provided. This sensor is a substrate having a magnet arranged so as to move in at least the first direction and a plurality of magnetoresistive elements arranged on the magnet, and the magnetoresistive element moves the magnet in the first direction. It comprises a substrate, which is arranged to detect. Here, the magnetoresistive elements are arranged in a bridge arrangement so as to compensate for the movement of the magnet in at least the second direction.

The present disclosure will then be described as just an example with reference to the accompanying drawings.

It is the schematic perspective view of the sensor by one Embodiment of this disclosure. It is a top view of the sensing element of the sensor of FIG. It is a bridge circuit according to one embodiment of the present disclosure. It is a chart which shows the transmission curve of the GMR spin valve by one Embodiment of this disclosure. 6 is a chart showing the magnetic field strength on the surface of the sensing element of FIG. 2 when the magnet is suspended above the sensing element. It is a top view of the sensing element by the further embodiment of this disclosure. It is a bridge circuit according to one embodiment of the present disclosure. 6 is a chart showing a magnetic field in each element of the sensing element of FIG. 6, and a chart showing a relative position between the magnet and the sensing element. 6 is a chart showing a magnetic field in each element of the sensing element of FIG. 6, and a chart showing a relative position between the magnet and the sensing element. 6 is a chart showing a magnetic field in each element of the sensing element of FIG. 6, and a chart showing a relative position between the magnet and the sensing element. 6 is a chart showing a magnetic field in each element of the sensing element of FIG. 6, and a chart showing a relative position between the magnet and the sensing element. It is a chart which shows the total magnetic field strength with respect to the movement of a magnet in the z direction. It is a bridge circuit according to a further embodiment of the present disclosure. It is a top view of the sensing element by the further embodiment of this disclosure. It is a bridge circuit according to a further embodiment of the present disclosure. It is a chart which shows the typical transfer curve of the GMR multilayer by one Embodiment of this disclosure. It is a chart which shows the magnetic field in each element of the sensing element of FIG. It is a chart which shows the magnetic field in each element of the sensing element of FIG. It is a chart which shows the magnetic field in each element of the sensing element of FIG. It is a chart which shows the magnetic field in each element of the sensing element of FIG. It is a chart which shows the total magnetic field strength with respect to the movement of the magnet in the z direction about the sensing element of FIG.

The position sensor typically includes a magnet suspended above the sensing element. The magnet generates a magnetic field, and the sensing element measures the magnetic field strength. The magnet may be suspended so that it can move back and forth with respect to the sensing element. For example, magnets may be suspended using metal connections that act as springs. As the magnet approaches the sensing element, the magnetic field strength at the sensing element increases accordingly. Conversely, as the magnet moves away from the sensing element, the magnetic field strength in the sensing element decreases accordingly. Therefore, the output of the sensing element is a measure of magnetic field strength. This represents the distance between the magnet and the sensing element. As an embodiment, the sensing element may be a Hall effect sensor such as a giant magnetoresistive (GMR) sensor or a magnetoresistive device.

The position sensor is manufactured so that the magnet can move only in the direction in which position detection is required. This is commonly referred to as the z direction. However, it is not always possible to completely prevent the magnet from moving left and right in the xy plane, that is, in a plane perpendicular to the detection direction. The magnetic field generated by the magnet changes not only depending on the distance from the end of the magnet in the z direction, but also on the left and right in the xy plane. Therefore, any lateral movement of the magnet to the left or right can cause a change in output at the sensing element. This can be misinterpreted as a movement in the main direction of movement, resulting in an incorrect position reading. In addition, if the sensor moves in the immediate vicinity of another device that generates magnetic fields, the sensing element can detect these magnetic fields. This can be misinterpreted as the movement of the device in the main direction.

In one embodiment of the present disclosure, the sensor comprises a pair of sensing elements arranged to compensate for movement in the xy plane or changes in the magnetic field due to an external magnetic field. This is achieved using a pair of magnetoresistive elements that can be connected together in a Wheatstone bridge arrangement. Each element in each pair of elements is positioned on the opposite side of the magnet and is equidistant from the magnet. The magnetic field strengths on both sides of the magnet are approximately equal but in opposite directions. The reluctance sensing elements are arranged such that each pair of elements is aligned and in the same direction in their sensing direction, that is, their sensitivities. Therefore, one of the elements has a very high electrical resistance and the other has a lower electrical resistance than when the magnet is in the center of the xy plane. As the magnet moves in the sensing direction in the xy plane, both elements in the pair will experience similar or identical changes in electrical resistance. Therefore, the potential divider ratio in the Wheatstone bridge, and thus the output of the Wheatstone bridge, remains the same or substantially the same.

By arranging two pairs of elements that have sensing directions perpendicular to each other in the xy plane and are evenly distributed around the magnet, the movement of the magnet in the xy plane is greatly compensated. Moreover, the application of a uniform external magnetic field, for example from an external device, will have no or minimal effect on the output of the Wheatstone bridge.

FIG. 1 shows a schematic perspective view of a position sensor 100 according to an embodiment of the present disclosure. As shown in FIG. 1, the sensor includes a magnet 101 and a sensing element 102. The magnet 101 is suspended above the sensing element 102 and is arranged so as to move in the main direction. In this embodiment, the main direction is the z direction, so that the magnets are arranged to move away from the sensing element 102 and towards the sensing element 102. However, the magnet can also move slightly in the xy plane. This is because it is very difficult to suspend the magnet in such a way that there is no movement in the xy plane while allowing movement in the z direction. For example, the magnet may be supported by a metal sheet connector that attaches the magnet to the sensor. The metal connector acts like a spring, thereby allowing movement in the z direction. However, since the metal connector is spring-shaped, a small amount of movement can occur in the xy plane.

FIG. 2 shows a plan view of the sensing element 102 shown in FIG. In this embodiment, the sensing element 102 includes a substrate 103 that can be made of silicon or glass. The substrate has four magnetoresistive elements R1, R2, R3, and R4 formed on the upper surface of the substrate 103. The magnetoresistive element is a thin film device, which can be formed using standard semiconductor manufacturing processes. In this embodiment, the magnetoresistive device is a giant magnetoresistive (GMR) spin valve. However, the magnetoresistive element may be a tunnel magnetoresistive element (TMR) element or an anisotropic magnetoresistive element (AMR). Generally, these devices may be referred to as xMR devices. In a further embodiment, any type of reluctance device that is sensitive to changes in the magnetic field in a particular direction may be used.

In this embodiment, the magnetoresistive elements R1 to R4 may be formed toward the respective corners of the square substrate. In this embodiment, the magnetoresistive elements at the opposite corners of the sensing element 102 are arranged so that their sensitivity directions are aligned. Therefore, the sensitivity directions of the elements R1 and R4 are aligned, and the sensitivity directions of the elements R2 and R3 are aligned. The sensitivity directions of the elements R2 and R3 are arranged so that they are perpendicular to the sensitivity directions of the elements R1 and R4. However, it will be understood that other arrangements are possible. For example, each of the magnetoresistive elements R1 to R4 may be formed toward the center of the edge of the substrate.

In a further embodiment, the sensing element may include more than two pairs of magnetoresistive elements. The greater the number of pairs of elements, the better the sensor is to compensate for the movement of the magnet in the xy plane. For a given number of pairs of magnetoresistive elements, the sensitivity directions of the pairs may be evenly distributed around 360 degrees. That is, the pairs of magnetoresistive elements can be evenly distributed around a plane in which motion is compensated, and each pair is positioned on the opposite side of the magnet and equidistant from the magnet.

FIG. 3 is a circuit diagram showing a mode in which magnetoresistive elements R1 to R4 can be connected in a bridge arrangement in order to detect a change in a magnetic field. In this embodiment, the elements R1 and R4 may be connected in series between the first node and the second node. The first node is connected to the first supply rail and the second node is connected to the second supply rail or ground. In the corresponding manner, the elements R3 and R2 are connected in series between the first node and the second node. Therefore, the combination of the elements R1 and R4 is connected in parallel with the combination of the elements R2 and R3. The output of the bridge circuit is then taken from a third node between elements R1 and R4 and a fourth node between elements R2 and R3. As the resistance of the device changes, the output changes, which can provide an indicator of the movement of the magnet in the z direction.

FIG. 4 shows a typical transmission curve of a GMR spin valve. This chart shows how the rate of change of the resistance of the device changes with respect to the applied magnetic field. The resistance is low with respect to the high positive magnetic field applied in the sensitivity direction of the GMR spin valve. The resistance is high against a high negative magnetic field applied in the sensitivity direction of the GMR spin valve. The magnetoresistive element of the above-described embodiment can take these characteristics.

FIG. 5 shows a magnetic field in the xy plane of the surface of the sensing element 102 when the magnet is located at a distance of 2 mm above the surface and is exactly in the center of the sensor surface, that is, when it does not move in the xy plane. Is shown. The chart shows the in-plane components (Hx and Hy) but does not include the out-plane components (Hz). The magnetic field strength is essentially zero at the very center of the sensor surface, whereas it is relatively strong towards the edge of the sensor.

Next, the operation of the sensor 100 will be described. Referring to the arrangement shown in FIG. 2, the resistance of R1 and R2 is low because a high magnetic field is applied in the same direction as the sensitivity direction of R1 and R2 while the magnet is in the steady state. On the contrary, since the high magnetic field is applied in the direction opposite to the sensitivity direction of R3 and R4, the resistance of R3 and R4 is high. This causes a voltage difference in the output of the bridge circuit. This voltage may be recorded as a preset voltage for zero movement in the z direction.

Assuming that the magnet 101 is fixed in the xy plane, the magnetic field strength weakens at the surface of the sensing element as the magnet moves away from the sensing element 102. Therefore, as the magnetic field is oriented in the same direction as the sensitivity direction of the elements R1 and R2, the resistance of the elements R1 and R2 increases. Conversely, as the magnetic field is oriented in the direction opposite to the sensitivity direction of the elements R3 and R4, the resistance of the elements R3 and R4 decreases. Therefore, the ratio of the resistances of the elements R1 and R4 decreases, while the ratio of the resistances of the elements R3 and R2 increases. Therefore, the output of the bridge circuit also changes. The opposite happens when the magnet moves towards the sensing element.

With reference to FIG. 2 again, the magnetoresistive element and the configuration of the bridge circuit are such that the movement of the magnet in the xy plane has a minimal or zero effect on the output of the bridge circuit. For example, when the magnet moves in the xy plane in the sensitivity direction of R1 and R4, the resistance values of R1 and R4 change accordingly. For example, referring to FIG. 5, as the magnet moves laterally towards R1, the magnetic field decreases slightly and the resistance increases slightly. As the magnet moves towards R1, the magnet moves away from R4. This causes a slight increase in the magnetic field at R4. However, since the magnetic field is in the direction opposite to the sensitivity direction of R4 and R4 is at high resistance, R4 also experiences a corresponding increase in resistance. As such, the R1 and R4 divider networks do not experience any significant changes in divider ratios. Therefore, the output from the bridge circuit remains the same or substantially the same. As a result of having two pairs of magnetoresistive elements, similar compensation for movement in other directions in the xy plane is achieved.

FIG. 6A shows the sensing element 600 according to a further embodiment. The sensing element 600 is the same as the element 102 shown in FIG. 2, except that the magnetoresistive elements H1 to H4 are positioned along the edge of the substrate instead of the corners. The arrows shown in FIG. 6A correspond to the sensitivity direction for each element. Therefore, in this embodiment, the magnetoresistive elements at the opposite ends of the sensing element 600 are arranged so that their sensitivity directions are aligned. The sensitivity directions of the elements H1 and H3 are aligned, and the sensitivity directions of the elements H2 and H4 are aligned. The sensitivity directions of the elements H2 and H4 are arranged so that they are perpendicular to the sensitivity directions of the elements H1 and H3. As for the bridge circuit, as shown in FIG. 6B, H1 and H3 are connected in series on one side of the bridge, and H2 and H4 are connected in series on the other side.

When the magnet moves in the z direction, the method of operation is essentially the same as described above in connection with FIGS. 2 and 3. While the magnet is in the steady state, the resistance of H1 and H2 is low because a high magnetic field is applied in the same direction as the sensitivity direction of H1 and H2. On the contrary, since the high magnetic field is applied in the direction opposite to the sensitivity direction of H3 and H4, the resistance of H3 and H4 is high. Therefore, as the magnet moves away from the sensing element 600, the magnetic field strength weakens on the surface of the sensing element, increasing the resistance of the elements H1 and H2 and decreasing the resistance of the elements H3 and H4. Therefore, the resistivity ratios of the elements H1 and H3 decrease, while the resistivity ratios of the elements H4 and H2 increase, resulting in a change in the output of the bridge circuit. As mentioned above, the opposite happens when the magnet moves towards the sensing element 600.

7A-7D show measurements of magnetic field strength at each individual element of the sensing element 600 to demonstrate how the sensor operates. In practice, no such measurement is made. FIG. 8 shows the overall output of the sensing element 600. Note that the charts shown in FIGS. 7 and 8 are based on a simulation in which the starting or zero position of the magnet in the z direction is about 2 mm from the magnet to the sensor surface. Therefore, the graphs shown in FIGS. 7A-7D and 8 show the change in magnetic field strength in the z direction as the magnet moves from this zero position towards and away from the sensor.

FIG. 7A shows the output of each element when the magnet is in the center of the sensing element. The position of the sensing element with respect to the magnet is shown on the right side of the chart. The y-axis shows the measured magnetic field strength, while the x-axis shows the displacement of the magnet in the z direction in millimeters. As shown in FIG. 7A, the magnetic field strengths measured in H1 and H2 are the same regardless of the displacement of the magnet in the z direction. The magnetic field strengths measured by H3 and H4 are also the same, and are equal to and opposite to the magnetic field strengths measured by H1 and H2. Therefore, as z increases, the magnetic field strength decreases at H1, H2, H3, and H4. Therefore, the output from the bridge circuit reflects only the movement in the z direction.

FIG. 7B shows the same arrangement when the magnet is displaced in the x direction (left in this example). As shown, the H2 and H4 plots do not change, or change to a very small extent, as the magnetic field strength does not change substantially in the H2 and H4 regions. However, the plot representing H1 is moving upwards, indicating an increase in magnetic field strength. The plot representing H3 is also moving upwards, representing a decrease in magnetic field strength. Therefore, the resistance of both H1 and H3 will be reduced. Since H1 and H3 are formed in series in a bridge arrangement, the potential between the two resistors will not change significantly. In effect, H1 and H3 compensate for movement in the x direction.

FIG. 7C shows the same arrangement when the magnet is displaced in the y direction (upward in this example). As shown, the plot of H1 and the plot of H3 do not change or change to a very small extent because the magnetic field strength does not change substantially in the region of H1 and H3. However, the plot representing H2 is moving upwards, showing an increase in magnetic field strength. The plot representing H4 is also moving upwards, representing a decrease in magnetic field strength. Therefore, the resistance of both H2 and H4 will be reduced. Since H2 and H4 are formed in series in a bridge arrangement, the potential between the two resistors will not change significantly. In effect, H2 and H4 compensate for movement in the y direction.

FIG. 7D shows the same arrangement when the magnets are displaced in the x and y directions. Here, the plot representing H1 shows an increase in magnetic field strength in the region of element H1, while the plot representing H3 shows a decrease in magnetic field strength in the region of element H3, whereby elements H1 and H3 correspond. Experience a decrease in resistance. Similarly, the plot representing H2 shows an increase in magnetic field strength in the region of element H2, while the plot representing H4 shows a decrease in magnetic field strength in the region of element H4. However, since the sensitivity directions of the elements H2 and H4 are perpendicular to the sensitivity directions of the elements H1 and H3, this change in magnetic field strength results in a corresponding increase in the resistance of the elements H2 and H4. As a result, the bridge outputs in each pair of elements H1 and H3 and each of the elements H2 and H4 remain the same or substantially the same. Therefore, H1 and H3 compensate for the movement in the x direction, and H2 and H4 compensate for the movement in the y direction.

FIG. 8 is a chart showing the magnetic field strength detected by the bridge circuit with respect to the displacement of the magnet in the z direction. In this embodiment, the charts are a plot when the magnet is in the center, a plot when the magnet is displaced 0.2 mm in the x direction, a plot when the magnet is displaced 0.2 mm in the y direction, and a plot in the x direction and the y direction. The plot when the displacement is 0.2 mm in both is shown. There is a slight difference in output due to xy motion, which is largely compensated for compared to single element detectors.

FIG. 9 shows a bridge circuit according to an alternative embodiment. In this embodiment, R1 to R4 are formed from two identical magnetoresistive elements R1a, R1b, R2a, R2b, R3a, R3b, R4a, and R4b, respectively. For example, R1a and R1b are formed by cutting the strip forming R1 in half. R1a and R1b have the same sensitivity direction and are located in the same part of the sensing element. Each of these elements is then connected in a bridge arrangement as shown in FIG. The advantage of this arrangement is that the temperature matching characteristics are improved. When the magnet moves in the z direction, the method of operation is essentially the same as described above in connection with FIGS. 2 and 3, and moving in the z direction causes a change corresponding to the output of the bridge circuit. Similar to FIGS. 2 and 3, any movement of the magnet in the xy plane is compensated by a pair of sensing elements on opposite sides of the sensor that are aligned and have sensitivities in the same direction. For example, each of the sensing element pairs R1a and R4b, R1b and R4a, R2a and R3b, R2b and R3a will compensate for the displacement in the xy plane.

FIG. 10 shows a sensing element 900 according to a further embodiment of the present disclosure. In the present embodiment, in addition to the magnetoresistive elements R1 to R4, a shielded reference resistor 901 is included in the center of the sensing element 900. In this embodiment, the magnetoresistive element is a GMR multilayer element. FIG. 11 shows a bridge arrangement used with the arrangement shown in FIG. R1 to R4 may be connected in series or in parallel. The total resistance of the series or parallel arrangement of R1 to R4 should be equal to or approximately equal to the resistance of the reference resistor 901. Each pair of elements, R1 and R4, and R2 and R3 compensate for movement in the xy plane in substantially the same way as in the previous embodiment. Alternatively, R1 to R4 may be formed from two identical magnetoresistive elements R1a, R1b, R2a, R2b, R3a, R3b, R4a, and R4b, respectively. In such a case, the upper left resistor of FIG. 11 may be formed from R1a to R4a, and the lower right resistor may be formed from R1b to R4b. As a further alternative, the upper left resistor may be formed from R1 and R2, while the lower right resistor may be formed from R3 and R4.

FIG. 12 is a chart showing a typical transfer curve of a GMR multilayer according to an embodiment of the present disclosure. In this example, the chart shows the general relationship between GMR resistance and magnetic field strength for the resistors disclosed herein. The change in resistance is independent of the magnetic field direction.

13A through 13D show simulations of individual magnetic field strength measurements of resistors R1 to R4 in a further embodiment. In this embodiment, the magnetoresistive element is arranged at the center of the edge rather than at the corner, similar to the arrangement shown in FIG. 6A. FIG. 14 shows a simulation of the output of the bridge arrangement shown in FIG. 11 using the reluctance arrangements used for FIGS. 13A-13D. As can be seen, this arrangement shows a further improvement over the embodiments described above, with little or no difference in the output resulting from movement in the xy plane.

FIG. 13A shows changes in the magnetic field strength of all four resistors R1 to R4 when the magnet is displaced in the z direction when it is in the upper center of the sensor, that is, when there is no displacement in the x and y directions. Is shown. Here, the magnetic field strengths of all four resistors are the same. 13B, 13C, and 13D show the change in magnetic field strength due to the displacement in the z direction when the magnet is also displaced laterally away from its central position. In FIG. 13B, the magnet is displaced in the x direction and the resistors R1 and R3 experience a corresponding change in magnetic field strength and thus resistance, thereby compensating for this lateral movement. In FIG. 13C, the magnet is displaced in the y direction and the resistors R2 and R4 experience a corresponding change in magnetic field strength and thus resistance, thereby compensating for this lateral movement. In FIG. 13D, the magnets are displaced in both the x and y directions, and each pair again experiences a corresponding change in magnetic field strength and thus resistance, thereby being responsible for lateral movement in both directions.

The present disclosure is suitable for use in many applications where detection of magnet movement in one direction can be hindered by movement in the other direction. Exemplary applications include digital camera drive motors, microscope drive motors, and proximity detectors.

100 Position sensor 101 Magnet 102 Sensing element 103 Board 900 Sensing element 901 Reference resistance

Claims (19)

A magnetoresistive position sensor for measuring a position in at least the first direction.
With magnets arranged to move at least in the first direction,
A differential magnetic field sensor arranged to detect the movement of the magnet in the first direction and to compensate for the movement of the magnet in at least the second direction .
Said at least second direction is in a first plane, said first plane, said that deviates relative to the first direction, the magnetoresistive position sensor. The sensor according to claim 1, wherein the differential magnetic field sensor includes a plurality of magnetoresistive elements. The sensor according to claim 2, wherein each of the plurality of magnetoresistive elements has a sensing direction, and at least the first pair of the magnetoresistive elements is arranged so that their sensing directions are aligned. Wherein the sensing direction of the plurality of magnetoresistive elements, the first being located in the plane A sensor according to claim 3. The sensor according to claim 4, wherein the first plane is substantially perpendicular to the first direction. Claim that the second pair of magnetoresistive elements is arranged so that their sensing directions are aligned and their sensing directions deviate from the first pair of magnetoresistive elements. The sensor according to 3. The sensor according to claim 6 , wherein the sensing direction of the first pair of the magnetoresistive element is substantially perpendicular to the sensing direction of the second pair of the magnetoresistive element. Wherein the plurality of magnetoresistive elements, the so small the first and second pairs even without the magnetoresistive element are distributed uniformly around the sensor, disposed in said first plane, said magnetoresistive The sensor according to claim 6 , wherein each element of the pair of elements is arranged on the opposite side of the sensor and at a position equal to the magnet. Wherein the plurality of magnetoresistive elements are connected in a bridge arrangement, the output of the bridge arrangement, showing the movement of the magnet in the first direction, the sensor according to claim 2. The sensor according to claim 9 , wherein the bridge arrangement is a Wheatstone bridge circuit. Said at least second direction is in a substantially perpendicular said first plane with respect to the first direction, the output of the bridge arrangement, the movement of the magnet in said first plane The sensor according to claim 9, which is not shown. The first pair of magnetoresistive elements is connected in series between the first node and the second node, and the second pair of elements is between the first node and the second node. The sensor according to claim 9 , wherein the output of the bridge circuit is taken from the node between each pair. Each of the plurality of magnetoresistive elements has a sensing direction, and the first pair of the magnetoresistive elements is arranged so that their sensing directions are aligned, and the second pair of the magnetoresistive elements. Are arranged so that their sensing directions are aligned, and the sensing direction of the second pair of the magnetoresistive elements is deviated from the sensing direction of the first pair of the magnetoresistive elements. a sensor according to claim 1 2. Wherein the sensing direction of the first pair of magnetoresistance elements are substantially perpendicular to the sensing direction of the second pair of the magnetoresistive element, the sensor according to claim 1 3. The sensor according to claim 2, wherein one of the plurality of magnetoresistive elements is a reference resistance. The sensor according to claim 15 , wherein the reference resistor is shielded so that its output is not magnetic field dependent. A method for measuring a position in at least a first direction using a reluctance position sensor.
Using a differential magnetic field sensor to detect the position of the magnet in the first direction,
Using the differential magnetic field sensor, viewed contains a compensating movement of the magnets in at least a second direction, and
A method in which the at least the second direction is in the first plane and the first plane is offset from the first direction . Before SL first plane is substantially perpendicular to the first direction, the method of claim 1 7. A magnetoresistive position sensor for measuring the position of at least a first direction,
With a magnet arranged to move at least in the first direction,
A substrate comprising a substrate having a plurality of magnetoresistive elements arranged on the substrate, wherein the magnetoresistive element is arranged so as to detect the movement of the magnet in a first direction.
The magnetoresistive element is arranged in a bridge arrangement so as to compensate for the movement of the magnet in at least the second direction, the at least the second direction is in the first plane, and the first plane is , it is offset with respect to the first direction, magnetoresistive position sensor.